Bad service

I want to report Pep cell in Jabulani mall , Soweto. I went there yesterday to buy a phone that takes two sim cards , Vodacom and Telkom network. The sales lady who assisted me sold me the Mobicel X1 and the phone it's MTN. I took the the phone to the office to connect since I will be working from home and it was poor service and I was advised that I must go back to the store to exchange the phone because it's poor in network. I tried to exchange the phone in Alberton and the told me to take it back to Jabulani mall and that the sales lady was wrong to sell the MTN phone to me at least if it was Vodacom.I drive back to Jabulani mall to return and the manager Phumzile was fuming , pointing the finger at me , refused to exchange the phone or given me money back. She ended up calling the security that she wants to close the shop and they must take me out

I feel betrayedqor mislead because the sold me the phone knowing that it's poor in service just to lift up theirs sales.

If there's was no problem with the Mobicel phone, why was the manager fuming, pointing the finger at me and refused to exchange the phone or give me money back?